The general rule is, that witnesses must testify to facts, and are not permitted to give their opinions .as evidence. One of the exceptions, however, to this rule, is, that medical men may be permitted to testify, or express their opinion, as to the character, or cause of disease, or the consequences that have, or probably will result, from wounds, and also as to the sanity of the mind, as collected from all the -circumstances. 1 Greenl. Ev. <§> 440.
But witnesses, whether medical men or not, are not permitted to give their opinions, or conclusions, unless such opinion, or conclusion, is an inference of skill, or the scientific result of given facts. 5 Porter, 339.
Dr. Ames could therefore have expressed his opinion, as to the character of the disease of which the slave died. He could also state, what in his opinion, would have been the .proper treatment of the disease, &c. But he could not be permitted to testify, how other physicians would have treated the disease, or how they might have treated it, owing to the *814doubtful nature of the disease, when at the same time he would have condemned such treatment. Whether they would, or would not, is matter purely of opinion, and not the result of scientific skill, from given facts. The court therefore erred, in permitting this portion of Dr. Ames’s testimony.
The greatest difficulty I have had in this case is, to ascertain what possible influence this testimony could have had on the mind of the jury, under the circumstances, as presented by the record. But inasmuch as we cannot see beyond doubt, but it may have done injury to the plaintiff; and as it was illegal, the judgment must be reversed, and the cause remanded.